Psoriasis is a skin condition characterised by itchy patches of thick, red skin with silvery scales. The patches usually appear on elbows, knees, scalps, backs, faces, palms, and feet, but they can also appear on other parts of the body. In some cases, people with psoriasis also develop arthritis called psoriatic arthritis.

Psoriasis is caused by an impaired immune system. Normal skin cells grow deep inside the skin and then rise to the surface during a process called cell turnover. This process normally takes a month. Your cells grow faster than this rate in psoriasis, sometimes within days.

Due to its overlapping appearance with other skin diseases, psoriasis can be difficult to diagnose. An examination under a microscope may be needed by your doctor.